U.S. patent application number 14/412361 was filed with the patent office on 2016-09-22 for an incident angle insensitive color filter and its manufacturing method.
The applicant listed for this patent is ZHEJIANG UNIVERSITY. Invention is credited to XU LIU, WEIDONG SHEN, CHENYING YANG, YUEGUANG ZHANG.
Application Number | 20160274282 14/412361 |
Document ID | / |
Family ID | 50501173 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160274282 |
Kind Code |
A1 |
SHEN; WEIDONG ; et
al. |
September 22, 2016 |
AN INCIDENT ANGLE INSENSITIVE COLOR FILTER AND ITS MANUFACTURING
METHOD
Abstract
An incident angle insensitive color filter is disclosed,
comprising a substrate, wherein several cylindrical gratings, made
of silicon, are arranged in a regular hexagon shape on the
substrate which is made up of fused quartz. A manufacturing method
of the aforesaid filters is also disclosed. Different from the
traditional chemical filters and traditional interference filters,
incident angle insensitive color filters in the present invention
are based on two-dimensional grating structure and make use of the
huge refractive index contrast in the grating layer, by which the
resonance is excited the resonance via the coupling between the
regions with high/low refractive index, so as to achieve the
incident angle insensitive filtering effects. The manufacturing
method of incident angle insensitive color filters in the present
invention is simple and of low cost, which is suitable for large
scale mass manufacture. Therefore, the present invention is
expected to be extensively applied in the fields of liquid crystal
display, color printing, sensor detecting, anti-counterfeiting and
so forth.
Inventors: |
SHEN; WEIDONG; (HANGZHOU,
ZHEJIANG PROVINCE, CN) ; YANG; CHENYING; (HANGZHOU,
ZHEJIANG PROVINCE, CN) ; ZHANG; YUEGUANG; (HANGZHOU,
ZHEJIANG PROVINCE, CN) ; LIU; XU; (HANGZHOU, ZHEJIANG
PROVINCE, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZHEJIANG UNIVERSITY |
Hangzhou City, Zhejiang |
|
CN |
|
|
Family ID: |
50501173 |
Appl. No.: |
14/412361 |
Filed: |
January 2, 2014 |
PCT Filed: |
January 2, 2014 |
PCT NO: |
PCT/CN2014/070002 |
371 Date: |
December 31, 2014 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 5/207 20130101;
G02B 5/1819 20130101; G02B 1/02 20130101; G02B 5/201 20130101 |
International
Class: |
G02B 5/20 20060101
G02B005/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2013 |
CN |
201310689440.8 |
Claims
1. An incident angle insensitive color filter, comprising a
substrate (2), wherein several cylindrical gratings (1), made of
silicon, are arranged in a regular hexagon shape on the substrate
(2) which is made of fused quartz.
2. The incident angle insensitive color filter as claimed in claim
1, wherein the gratings (1) are perpendicular to the substrate (2);
the thickness of the gratings (1) is 70-200 nm; the cylindrical
radius of the gratings (1) is 40-90 nm; and the center distance
between the cylindrical gratings (1) is 100-280 nm.
3. A manufacturing method of the incident angle insensitive color
filter as claimed in claim 1, wherein the following steps are
comprised: (1) obtaining the thickness, the cylindrical radius and
the center distance of cylindrical gratings corresponding to the
central wavelength of the filter to be fabricated by optimization;
(2) depositing a layer of silicon on the fused quartz substrate and
anneal, wherein the thickness of the silicon layer equals to the
thickness of the grating; (3) preprocessing the aluminum foil; (4)
anodizing the preprocessed aluminum foil twice and obtaining
orderly arranged porous alumina, wherein the pore radius equals to
the cylindrical radius of gratings and the pore center distance
equals to the center distance of cylindrical gratings; (5)
spin-coating a layer of polymethyl methacrylate on the porous
alumina as the protective layer for removing the aluminum
substrate; (6) removing the aluminum substrate in the mixed
solution of copper sulfate and hydrochloric acid, clean and obtain
a porous alumina template frame coated with a protective layer; (7)
using oxygen plasma to bombard the silicon layer with fused quartz
substrate, and then fix the porous alumina template frame onto the
silicon layer with fused quartz substrate in step (2); (8) removing
the polymethyl methacrylate layer on the porous alumina template
frame; (9) atomic layer depositing oxide on the orderly arranged
porous alumina template frame; (10) using reactive ion etching to
remove the oxide layer covered on the surface of porous alumina;
(11) using KOH solution to remove the porous alumina template
frame, showing the outline of the required two-dimensional grating
which is composed of cylindrical oxide columns orderly arranged in
a regular hexagon shape; (12) using reactive ion etching to etch
the oxide columns and the silicon layer simultaneously, transfer
the two-dimensional grating template to the bottom silicon layer,
thus the required two-dimensional grating is made. Then use wet
etching to remove the residual oxide columns and obtain an incident
angle insensitive color filter, wherein the gratings are
cylindrical, arranged in regular hexagon and made up of
silicon.
4. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 3, wherein the annealing conditions in
step (2) are: rapid annealing under 1000-1100.degree. C. for 15-25
seconds first, then annealing under 550-650.degree. C. for 20-25
hours, and at last annealing under 850-950.degree. C. for 15-25
hours.
5. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 4, wherein the annealing conditions in
step (2) are: rapid annealing under 1050.degree. C. for 20 seconds
first, then annealing under 600.degree. C. for 24 hours, and at
last annealing under 900.degree. C. for 20 hours.
6. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 3, wherein the aluminum foil in step (3)
is high purity aluminum foil of 99.999%.
7. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 3, wherein the oxides are titanium
dioxide, hafnium dioxide or tantalum pentoxide.
8. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 7, wherein the oxides are titanium
dioxide.
9. The manufacturing method of the incident angle insensitive color
filter as claimed in claim 3, wherein the reactive ion etching
conditions in step (12) are: the volume flow rate of carbon
tetrafluoride is 20-30 sccm, and the volume flow rate of oxygen is
3-6 sccm.
10. The manufacturing method of the incident angle insensitive
color filter as claimed in claim 9, wherein the reactive ion
etching conditions are: the volume flow rate of carbon
tetrafluoride is 25 sccm, and the volume flow rate of oxygen is 3.1
sccm.
11. A manufacturing method of the incident angle insensitive color
filter as claimed in claim 2, wherein the following steps are
comprised: (1) obtaining the thickness, the cylindrical radius and
the center distance of cylindrical gratings corresponding to the
central wavelength of the filter to be fabricated by optimization;
(2) depositing a layer of silicon on the fused quartz substrate and
anneal, wherein the thickness of the silicon layer equals to the
thickness of the grating; (3) preprocessing the aluminum foil; (4)
anodizing the preprocessed aluminum foil twice and obtaining
orderly arranged porous alumina, wherein the pore radius equals to
the cylindrical radius of gratings and the pore center distance
equals to the center distance of cylindrical gratings; (5)
spin-coating a layer of polymethyl methacrylate on the porous
alumina as the protective layer for removing the aluminum
substrate; (6) removing the aluminum substrate in the mixed
solution of copper sulfate and hydrochloric acid, clean and obtain
a porous alumina template frame coated with a protective layer; (7)
using oxygen plasma to bombard the silicon layer with fused quartz
substrate, and then fix the porous alumina template frame onto the
silicon layer with fused quartz substrate in step (2); (8) removing
the polymethyl methacrylate layer on the porous alumina template
frame; (9) atomic layer depositing oxide on the orderly arranged
porous alumina template frame; (10) using reactive ion etching to
remove the oxide layer covered on the surface of porous alumina;
(11) using KOH solution to remove the porous alumina template
frame, showing the outline of the required two-dimensional grating
which is composed of cylindrical oxide columns orderly arranged in
a regular hexagon shape; (12) using reactive ion etching to etch
the oxide columns and the silicon layer simultaneously, transfer
the two-dimensional grating template to the bottom silicon layer,
thus the required two-dimensional grating is made. Then use wet
etching to remove the residual oxide columns and obtain an incident
angle insensitive color filter, wherein the gratings are
cylindrical, arranged in regular hexagon and made up of silicon.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an optical component,
particularly to an incident angle insensitive color filter and its
manufacturing method which can be applied in the fields of liquid
crystal display, color printing, sensor detecting,
anti-counterfeiting and so forth.
BACKGROUND OF THE INVENTION
[0002] Angle insensitive color filters have significant application
prospects in the fields of liquid crystal display, color printing,
sensor detecting, anti-counterfeiting and so forth. The traditional
chemical dye color filters achieve the filtering effect as the
result of a wavelength-selective absorption of the particular
functional groups. However, dyes will cause a material instability
and a significant environmental burden. The optical thin film
filters by multi-layer interference performs well with a high peak
transmittance, a tailored bandwidth, and stable specifications.
However, they present an obvious blue-shift phenomenon, that is,
spectral curves will move to short wavelengths with an increasing
angle of incidence, which limits the application at large incidence
angles. In recent years, a variety of color filters based on
sub-wavelength structures have been proposed owing to the intensive
research on the electromagnetic theory of subwavelength grating and
the development of micro/nano fabricating techniques. The guided
mode resonance light filters are able to switch the energy of the
incident light between reflection and transmission in a very small
range via the coupling between the high-order leaky mode and the
waveguide mode in the media of grating, so as to obtain the filters
with ultra-narrow band. However, the guided mode resonance filters
are very sensitive to the incidence angle. Even though the incident
angular tolerance can be improved via structure optimization and
other means, it is still very difficult to get higher insensitivity
of the incidence angle. By fabricating one-dimensional
subwavelength grating of silicon on the quartz substrates, Kanamori
et al obtained transmission color filters in the three colors of
red, green and blue. But their properties will change with the
incidence angle (Fabrication of transmission color filters using
silicon subwavelength gratings on quartz substrates, IEEE Photon.
Technol. Lett. 18, 2126-2128 (2006)). In addition, researchers also
proposed stacked subwavelength grating structure to obtain the
color filters with better performance at normal incidence by
stacking two layers of one-dimensional or two-dimensional
subwavelength gratings. To improve the insensitivity of the
incidence angle, Cheong et al proposed the use of silicon with high
refractive index as the material of two-dimensional subwavelength
grating to realize intense modulated grating and obtain high
angular tolerant reflective filters (High angular tolerant color
filter using subwavelength grating, Appl. Phys. Lett. 94, 213104-3
(2009)). However, their properties deteriorate at different azimuth
angles and are not suitable for practical application. Besides, the
electron beam lithography technique is used in the manufacturing
process. It is high cost, time-consuming, and difficult to
manufacture.
[0003] Among the nano-material structures, orderly porous structure
periodically arranged is widely studied and applied in numerous
research fields. Porous alumina, with pores regularly hexagonally
latticed, has attracted more and more researchers to study into
thoroughly and widely due to its simple and convenient
manufacturing methods. At present, the study of porous alumina
concentrates mainly focuses on the material characteristics and the
application of the physical structure of the material, such as the
producing of the nanotube, the transfer of the porous structure,
the observation of quantum dot structure, and so forth.
[0004] Atomic layer deposition (ALD) technology is a method of
forming a film by alternately feeding gas precursor pulse into the
reactor to absorb and have chemical reaction on the deposition
substrate. It was proposed by a scientist from Finland in 1970s.
With development of the microelectronics and deep submicron chip
technology in the middle of 1990s, ALD has been extensively applied
in the field of semiconductor. Due to the self-confinement of ALD
surface reaction, theoretically, the deposition accuracy of ALD can
reach atomic level. Furthermore, compared with the traditional
deposition method for an optical film, the film by ALD has
incomparable advantages in term of deposition temperature,
aggregation density and conformality. So the use of ALD in the
preparation of optical films gradually becomes a hot topic in
research.
[0005] Although research and application based on the combination
of porous alumina and atomic layer deposition has been proposed
constantly, as far as we know, the research on the manufacturing of
incident angle insensitive color filters by using atomic layer
deposition to fill the porous alumina with the high refractive
index oxides as the template has never been proposed. The
manufacturing of incident angle insensitive color filters in the
present invention is simple and of low cost. Therefore, the present
invention is expected to be extensively applied in the fields of
liquid crystal display, color printing, sensor detecting and
anti-counterfeiting and so forth.
SUMMARY OF THE INVENTION
[0006] The present invention relates to an incident angle
insensitive color filter which has a simple structure of
two-dimensional grating structure. It is insensitive to the
incidence angle, stable and environment friendly.
[0007] The present invention also relates to a manufacturing method
of such incident angle insensitive color filter. By combining the
porous alumina preparation technique and the atomic layer
deposition technique together, this method avoids such complicated
techniques as electron beam lithography, laser direct writing or
nanoimprint. It is simple and suitable for industrial
manufacture.
[0008] To solve the first technical problem, the present invention
provides the following technical solution:
[0009] an incident angle insensitive color filter, comprising a
substrate made of fused quartz, a plurality of cylindrical gratings
made of silicon, arranged in regular hexagon on the substrate.
[0010] The use of cylindrical gratings arranged in regular hexagon
ensures the insensitivity to the incidence angle of the light
filters and the filters in the present invention is suitable for
various situations with large incidence angles.
[0011] The light filters in the present invention are mainly
applied for visible light with wavelength ranging 380-780 nm. For
the required central wavelength, the filters of gratings with
different dimension can be designed. It is preferred that the
gratings as claimed are perpendicular to the substrate; the
thickness of the gratings is 70-200 nm; the radius of cylindrical
the gratings is 40-90 nm; and the center distance between the
cylindrical gratings is 100-280 nm.
[0012] To solve the second technical problem, the present invention
also provides a manufacturing method of the incident angle
insensitive color filters as claimed, comprising the following
steps:
[0013] (1) obtaining the thickness, the cylindrical radius and the
center distance of cylindrical gratings by optimization,
corresponding to the central wavelength of the filter to be
manufactured; and prior arts can be selected and used in the
optimization process;
[0014] (2) depositing a layer of silicon on the fused quartz
substrate and annealing, wherein the thickness of the silicon layer
equals to the thickness of the grating;
[0015] (3) preprocessing the aluminum foil;
[0016] (4) anodizing the preprocessed aluminum foil twice and
obtaining orderly arranged porous alumina, wherein the pore radius
equals to the radius of cylindrical gratings and the pore center
distance equals to the center distance of cylindrical gratings; in
this step, the pore depth shall meet the etching requirements in
step (12); and the porous alumina obtained in this step comprises
the porous alumina part with porous structure and an aluminum
substrate without porous structure;
[0017] (5) spin-coating a layer of polymethyl methacrylate on the
porous alumina as the protective layer for removing the aluminum
substrate;
[0018] (6) removing the aluminum substrate in the mixed solution of
copper sulfate and hydrochloric acid, clean and obtaining a porous
alumina template frame coated with a protective layer;
[0019] (7) using oxygen plasma to bombard the silicon layer with
fused quartz substrate, and then fixing the porous alumina template
frame onto the silicon layer with fused quartz substrate in step
(2);
[0020] (8) removing the polymethyl methacrylate layer on the porous
alumina template frame;
[0021] (9) atomic layer depositing oxide on the orderly arranged
porous alumina template frame;
[0022] (10) using reactive ion etching to remove the oxide layer
covered on the surface of porous alumina;
[0023] (11) using KOH solution to remove the porous alumina
template frame, showing the outline of the required two-dimensional
grating which is composed of cylindrical oxide columns orderly
arranged in regular hexagon;
[0024] (12) using reactive ion etching method to etch on the oxide
columns and the silicon layer simultaneously, transferring the
two-dimensional grating template to the bottom silicon layer, thus
the required two-dimensional grating is made, then using wet
etching to remove the residual oxide columns and obtaining an
incident angle insensitive color filter wherein the gratings are
cylindrical, arranged in regular hexagon and made up of
silicon.
[0025] In step (2), to make gratings with higher reflectivity, it
is preferred that the annealing conditions are follows: rapid
annealing under 1000-1100.degree. C. for 15-25 seconds first, then
annealing under 550-650.degree. C. for 20-25 hours, and at last
annealing under 850-950.degree. C. for 15-25hours. It is further
preferred that the annealing conditions are: rapid annealing under
1050.degree. C. for 20 seconds first, then annealing under
600.degree. C. for 24 hours, and at last annealing under
900.degree. C. for 20 hours.
[0026] To obtain regular, cylindrical pore structure, it is
preferred that the aluminum foil in step (3) is high purity
aluminum foil of 99.999%. If there is too much impurity in the
aluminum foil, the obtained cylindrical pore structure might be
irregular, which is bad for the subsequent manufacturing of
gratings.
[0027] The oxides as claimed are titanium dioxide, hafnium dioxide
or tantalum pentoxide which are all non-toxic, environment-friendly
and can be easily removed in the subsequent steps. It is further
preferred that the oxide is titanium dioxide.
[0028] To obtain the target grating structure, it is preferred that
the reactive ion etching conditions as claimed in step (10) are:
the volume flow rate of CHF.sub.3 is 50-60 sccm, and the volume
flow rate of O.sub.2 is 5-10 sccm; and it is further preferred that
the volume flow rate of CHF.sub.3 is 55 sccm, and the volume flow
rate of O.sub.2 is 5 sccm.
[0029] It is preferred that the reactive ion etching conditions as
claimed in step (12) are: the volume flow rate of carbon
tetrafluoride is 20-30 sccm, and the volume flow rate of oxygen is
3-6 sccm. After reactive ion etching, transfer the two-dimensional
grating to the bottom silicon layer and the upper oxide columns are
etched, then remove the residual oxide columns and the required
two-dimensional grating structure can be obtained. It is further
preferred that the reactive ion etching conditions are: the volume
flow rate of carbon tetrafluoride is 25 sccm, and the volume flow
rate of oxygen is 3.1 sccm.
[0030] Different from the traditional chemical light filters and
traditional interference light filters, incident angle insensitive
color filters in the present invention are based on two-dimensional
grating structure and make use of the huge refractive index
contrast in the grating layer, by which the resonance is excited
the resonance via the coupling between the regions with high/low
refractive index, so as to achieve the incident angle insensitive
filtering effects.
[0031] Compared with the prior art, the present invention has the
following advantages:
[0032] (1) Incident angle insensitive color filters in the present
invention, based on the porous alumina structure, control the pore
size and the thickness of the oxide with high refractive index by
atomic layer deposition via simple operations, to make specific
two-dimensional gratings and therefore fabricate incident angle
insensitive color filters. This method subtly combines the porous
alumina preparation and atomic layer deposition technique, and
successfully avoids such complicated techniques as electron beam
lithography, laser direct writing or nanoimprint, which is suitable
for large scale mass manufacturing and thus greatly reduces the
cost of the incident angle insensitive color filters.
[0033] (2) The manufacturing method of incident angle insensitive
color filters in the present invention is simple and of low cost,
which is suitable for large scale mass manufacturing. Therefore,
the present invention is expected to be extensively applied in the
fields of liquid crystal display, color printing, sensor detecting,
anti-counterfeiting and so forth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1a shows the schematic view of the structure of the
incident angle insensitive color filter in the present
invention.
[0035] FIG. 1b shows the arrangement diagram of gratings of the
light filter in FIG. 1a.
[0036] FIG. 2 shows the flow chart for the manufacturing method of
the incident angle insensitive color filter in the present
invention.
[0037] FIG. 3 shows the reflection spectrum chart of the blue light
filter designed in the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] Next, the present invention will be further described in
details with reference to the drawings.
[0039] As shown in FIGS. 1a and 1b, an incident angle insensitive
color filter comprises a substrate 2 and a single layer of
two-dimensional gratings 1 fixed on the substrate 2, wherein the
gratings 1 are cylindrical, made of silicon and arranged in a
regular hexagon shape on the substrate of fused quartz. Different
from the traditional chemical light filters and traditional
interference light filters, incident angle insensitive color
filters in the present invention are based on two-dimensional
grating structure and make use of the huge refractive index
contrast in the grating layer, by which the resonance is excited
the resonance via the coupling between the regions with high/low
refractive index, so as to achieve the incident angle insensitive
filtering effects.
[0040] As shown in FIG. 2, a manufacturing method of incident angle
insensitive color filters comprises the following steps:
[0041] (1) For expected color filters with specific central
wavelength, through the optimization of structural parameters,
corresponding thickness, cylindrical radius and center distance of
cylindrical gratings can be designed, wherein the thickness of the
gratings generally is 70-200 nm; the radius of the cylindrical
gratings is generally 40-90 nm; and the center distance among the
cylindrical gratings is generally 100-280 nm. Please see the
references for the optimization process: Chenying Yang, Liang Hong,
Weidong Shen, Yueguang Zhang, Xu Liu, and Hongyu Zhen, Design of
reflective color filters with high angular tolerance by particle
swarm optimization method, Opt. Express 21, 9315-9323 (2013).
[0042] (2) Depositing a layer of silicon on the clean fused quartz
substrate 2 by electron beam evaporation, form the silicon layer 3,
and have rapid annealing under 1050.degree. C. for 20 seconds
first, then annealing under 600.degree. C. for 24 hours, and at
last annealing under 900.degree. C. for 20 hours. Gratings
fabricated under such conditions will have high reflectance,
wherein the deposition thickness equals to the thickness of the
grating;
[0043] (3) Degrease the high-purity aluminum foil 4 (99.999%) in
acetone and ethyl alcohol, wash it in water, and then electropolish
it in the mixed solution of H.sub.4ClO.sub.4 and absolute ethyl
alcohol (1:3) under 16.about.18V at 10.degree. C. for 3 minutes.
Then, wash the polished aluminum foil with deionized water.
[0044] (4) First anodization: using 0.3 mol/L oxalic acid solution
as the electrolyte, controlling the oxidation electrode voltage
kept at 40V, oxidizing for 10 hours and washing with deionized
water; secondary anodization: soaking in the mixed solution of 6%
H.sub.3PO.sub.4 and 1.5% H.sub.2CrO.sub.4 (mass ratio) to remove
the oxide layer generated in the first anodization and washing with
deionized water. Then, putting it into 0.3 mol/L oxalic acid
solution again with the oxidation time determined based on the
required pore depth. Since the oxidation time is directly related
to the pore depth, their relation can generally be determined via
several tests. These operations are prior arts and the actual
oxidation time shall be determined based on the results of several
tests. And controlling the oxidation electrode voltage can change
the pore diameter of the porous alumina and the oxidation electrode
voltage is directly related to the pore diameter of the anodic
alumina. Their relation can generally be determined via several
tests. These operations are prior arts and the actual oxidation
time shall be determined based on the results of several tests.
After oxidation, washing it with deionized water and porous alumina
5 orderly arranged at subwavelength level can be obtained, wherein
the pore radius equals to the radius of cylindrical gratings and
the center distance of pores equals to the center distance of
cylindrical gratings. The porous alumina 5 comprises the porous
alumina part with porous structure and an aluminum substrate
without porous structure.
[0045] (5) Spin-coating a layer of polymethyl methacrylate 6 on the
porous alumina part with porous structure of the porous alumina 5,
specifically, 700 r/s spin coating for 9 seconds, 3000 r/s spin
coating for 30 seconds and drying under 90.degree. C. for 30
minutes, as the protective layer for removing the aluminum
substrate 7;
[0046] (6) Soaking in the mixed solution of 0.1 mol copper sulfate
and (mass ratio) 10% hydrochloric acid (volume of the hydrochloric
acid shall make sure the porous alumina 5 immersed) for 30-40
minutes, remove the aluminum substrate, clean and obtain the porous
alumina template frame 8 coated with a protective layer;
[0047] (7) Using oxygen plasma to bombard the substrate (O.sub.2
flow rate: 80 sccm, pressure: 80 mTorr, and power: 150W), and then
put the porous alumina onto the silicon layer 3 with fused quartz
substrate in step (2) for bonding under the action of Van der Waals
force;
[0048] (8) Conducting treatment with ultraviolet light and ozone
under 200.degree. C. for 30 minutes, then washing with acetone and
deionized water, and then removing the top polymethyl
methacrylate;
[0049] (9) Atomic layer depositing the oxide layer 9 with high
refractive index on the orderly arranged porous alumina template
frame 8, wherein the deposition thickness is equal to or greater
than the radius of cylindrical gratings. The filled oxide with high
refractive index by atomic layer deposition is titanium dioxide
(TiO.sub.2), or may be hafnium dioxide or tantalum pentoxide as
required. These solvents are non-toxic and can be easily removed.
Putting the prepared porous alumina template frame 8 into the
atomic layer deposition device and using titanium tetrachloride
(TiCl.sub.4) and H.sub.2O as the precursor for preparing titanium
dioxide (TiO.sub.2). During the reaction process, the temperature
of the precursor is kept constant at 20.degree. C., the temperature
of the porous alumina substrate is 120.degree. C., and the vacuum
degree of the reaction chamber is 3 mbar. The pulsing time of
titanium tetrachloride (TiCl.sub.4) and H.sub.2O is both 400 ms and
the purging time is both 5 seconds. The deposition thickness can be
controlled via the number of cycles.
[0050] (10) Using reactive ion etching (CHF.sub.3 volume flow rate:
55 sccm, and O.sub.2 volume flow rate: 5 sccm) to remove the oxide
layer 9 with high refractive index covered on the porous alumina
surface;
[0051] (11) Soaking in 1 mol KOH solution for 15 minutes to remove
the porous alumina 8 and the outline of the required
two-dimensional gratings (oxide columns 10) appears, which are
cylindrical, arranged in regular hexagon and made up of oxides with
high refractive index;
[0052] (12) Using reactive ion etching (CF.sub.4 volume flow rate:
25 sccm, and O.sub.2 volume flow rate: 3.1 sccm) on the oxide
columns 10 and the silicon layer 3 simultaneously, transferring the
two-dimensional grating to the bottom silicon layer, then using wet
etching to remove the residual oxide columns, thus the required
two-dimensional grating 1 is made, and obtaining an incident angle
insensitive color filter, wherein gratings 1 are cylindrical,
arranged in regular hexagon and made of silicon.
[0053] Taking the following incident angle insensitive color filter
as an example, for a blue filter with expected central wavelength
.lamda.=440 nm, its corresponding thickness of the silicon grating
is 91 nm; the cylindrical radius of the grating is 48 nm; the
center distance of the cylindrical grating is 119 nm; the pore
radius of the porous alumina is 48 nm; the pore center distance is
119 nm; the thickness of the oxides with high refractive index by
atomic layer deposition is 48 nm; and the cycle of atomic layer
deposition is 805. The specific method is same with the
manufacturing method of incident angle insensitive color filters in
the specific embodiment. The reflection spectrum tests of obtained
incident angle insensitive color filters is carried out at
incidence angle of 0.degree., 15.degree., 30.degree., 45.degree.
and 60.degree. respectively with the test results as shown in FIG.
3. According to FIG. 3, filters in the present invention are
insensitive to the incidence angle.
* * * * *